Foldable Chair

ABSTRACT

A foldable chair includes a foldable frame and a reinforcing joint. The foldable frame includes a supporting frame and a seat frame pivotally connected with each other via the reinforcing joint, wherein the reinforcing joint includes a first joint member, a second joint member, and a connecting member connecting the second joint member with the first joint member. The first joint member, having an engaging cavity, is coupled at the seat frame. The second joint member is coupled at the supporting frame and is received at the engaging cavity to frictionally couple with the first joint member. The reinforcing joint serves as a supporting shaft to support between the supporting frame and the seat frame and serves as a rotatable shaft to enable the second joint member to be rotated at the first joint member for a pivotal movement between the supporting frame and the seat frame.

NOTICE OF COPYRIGHT

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to any reproduction by anyone of the patent disclosure, as itappears in the United States Patent and Trademark Office patent files orrecords, but otherwise reserves all copyright rights whatsoever.

BACKGROUND OF THE PRESENT INVENTION Field of Invention

The present invention relates to a foldable chair, and more particularlyto a foldable chair with a reinforcing joint that not only supports thefoldable structure between a supporting frame and a seat frame of thefoldable chair but also ensures the loading force at the seat frame tobe evenly and efficiently distributed to the supporting frame.

Description of Related Arts

With present furniture manufacturing technology, a variety of foldablestructure is used in the furniture because the furniture can be foldedup as a portable furniture such that it is convenient for people totransport the furniture and it needs less room for storage. Therefore,the foldable furniture, such as foldable chair or table, is consideredas a common tool being used at homes, offices, and during camping.Accordingly, the foldable furniture is constructed by a plurality ofmetal construction tubes pivotally connected with other in such a mannerthat the foldable furniture is capable of folding into a compact sizeand unfolding to expanse its supporting size by means of the pivotmovement of the metal construction tubes.

For example, a conventional foldable chair comprises a support frame anda seat frame pivotally coupled at the support frame. In particular, thesupport frame comprises a front leg and a rear leg pivotally coupledwith the seat frame. It is worth mentioning that the front leg, the rearleg, and the seat frame are formed with the construction tubes, whereinthe construction tubes are pivotally connected together where they crossvia a rivet so that the foldable chair can be easily unfolded to providea rigid cross-support for use and be folded up for storage. Accordingly,a space must be provided between the two construction tubes in order toenable the pivotal movement between the construction tubes via therivet. As a result, the rivet not only enables the pivotal movementbetween the construction tubes but also allows an unwanted lateralmovement therebetween. This unwanted lateral movement will cause theunstable of the foldable chair when the foldable chair is moved at theunfolded position for supporting the loading force, i.e. when the usersits on the foldable chair. Accordingly, a washer is placed at the spacebetween the two construction tubes to minimize the distancetherebetween. In fact, when the user sits on the foldable chair, theweight of the user will substantially distribute to the support framethrough the rivets. Therefore, the rivets must be strong enough tosupport the loading force. Once the rivet is deformed, bent, or evenbroken by the loading force, the foldable chair cannot be pivotallyfolded or unfolded. In the worst case, the foldable chair will becollapsed.

In addition, the rivet passes through rivet holes formed at theconstruction tubes for pivotally connection therebetween, wherein thediameter of the rivet hole must be larger than a diameter size of therivet in order to allow the rivet to pass through the rivet hole.Therefore, a clearance is formed between the rim of the rivet hole andthe rivet. In other words, the clearance not only allows the rivet torotate within the rivet hole for pivotally moving the construction tubesbut also allows the rivet to laterally move within the rivet hole. As aresult, the clearance will cause the wobbling movement of the foldablechair when it is unfolded.

In addition, during the folding and unfolding movements, frictionalforces are unavoidably created between the rim of the rivet hole and therivet. Therefore, stress will be accumulated at the rim of the rivethole to cause the deformation of the rivet hole. The size of the rivethole will become bigger and bigger to affect the pivotal movement of theconstruction tubes. As a result, the conventional rivet cannot provide arigid configuration to support the connections of the foldable chair andwill only shorten the service life span of the foldable chair.

SUMMARY OF THE PRESENT INVENTION

The invention is advantageous in that it provides a foldable chair,wherein the foldable chair comprises a reinforcing joint for pivotallyconnecting a supporting frame with a seat frame to enhance thestabilization of the foldable chair.

Another advantage of the invention is to provide a foldable chair,wherein the reinforcing joint not only serves as a supporting shaft tosupport between the supporting frame and the seat frame but also servesas a rotatable shaft to enable the second joint member to be rotated atthe first joint member for a pivotal movement between the supportingframe and the seat frame.

Another advantage of the invention is to provide a foldable chair,wherein the reinforcing joint is able to effectively distribute theloading force at the seat frame to the supporting frame without damagingthe connection between the seat frame and the supporting frame.

Another advantage of the invention is to provide a foldable chair,wherein the reinforcing joint can retain a distance between the seatframe and the supporting frame to prevent any unwanted lateral movementtherebetween during the folding and unfolding operations.

Another advantage of the invention is to provide a foldable chair,wherein the first and second joint members are frictionally engaged witheach other to enhance the support of the reinforcing joint between theseat frame and the supporting frame. In particular, no clearance isformed between the first and second joint members to prevent anywobbling movement of the foldable chair especially when it is unfolded.

Another advantage of the invention is to provide a foldable chair,wherein the foldable chair is able to move between a folded position andan unfolded position via the reinforcing joint, wherein the first jointmember is rotated along the second joint member at a direction to movethe seat frame to the folded position, and in other words, the firstjoint member is rotated along the second joint member at an oppositedirection to move the seat frame to the unfolded position.

Another advantage of the invention is to provide a foldable chair,wherein two joint stoppers are coupled at an upper end of the rear legframe to provide multiple functions of retaining the foldable chair atthe unfolded position by biasing the joint stoppers against the backsupporting members of the foldable chair and retaining the foldablechairs at a stacked position by engaging with the joint stoppers withthe back supporting members of another foldable chair.

Another advantage of the invention is to provide a foldable chair,wherein the joint stopper can be incorporated with any existing foldingchair to provide the multiple functions.

Another advantage of the invention is to provide a foldable chair,wherein the seat panel is ergonomically design to ensure the sittingposture of the user.

Another advantage of the invention is to provide a foldable chair,wherein the and thigh supporting portion of the seat panel issuspendedly supported by the seat frame to provide a predeterminedflexibility so as to generate an upward bounding force to the thighs ofthe user.

Another advantage of the invention is to provide a foldable chair,wherein the foldable frame further comprises two guiding frames to guidethe rear legs of the foldable frame to overlap or expand with respect tothe front legs, so as to prevent unexpectedly horizontal movementhappened on the rear legs.

Another object of the present invention is to provide a foldable chair,which does not require altering the original structural design of thefoldable chair, so as to minimize the manufacturing cost of the foldablechair incorporating with the reinforcing joint. The reinforcing jointcan also incorporated with different foldable furniture such as afoldable table.

Another object of the present invention is to provide a reinforcingjoint for foldable chair, wherein no expensive or complicated structureis required to employ in the present invention in order to achieve theabove mentioned objects. Therefore, the present invention successfullyprovides an economic and efficient solution for providing a rigidconfiguration for the foldable chair.

Additional advantages and features of the invention will become apparentfrom the description which follows, and may be realized by means of theinstrumentalities and combinations particular point out in the appendedclaims.

According to the present invention, the foregoing and other objects andadvantages are attained by a foldable chair which comprises a foldableframe and at least one reinforcing joint.

The foldable frame is constructed by a plurality of construction tubes,wherein the foldable frame comprises a supporting frame and a seatframe.

The reinforcing joint is arranged for pivotally connecting one of theconstruction tubes of the supporting frame with one of the constructiontubes of the seat frame, wherein the reinforcing joint comprises a firstjoint member, a second joint member, and a connecting member extendedfrom the second joint member through the first joint member to ensure anengagement therebetween.

The first joint member, having an engaging cavity, is coupled at theseat frame. The second joint member is coupled at the supporting frameand is received at the engaging cavity to frictionally couple with thefirst joint member. Accordingly, the first and second joint membersserve as a supporting shaft to support between the supporting frame andthe seat frame and serve as a rotatable shaft to enable the second jointmember to be rotated at the first joint member for a pivotal movementbetween the supporting frame and the seat frame.

In accordance with another aspect of the invention, the presentinvention comprises a reinforcing joint for pivotally connecting firstand second construction tubes of a foldable chair, comprising:

a first joint member, having an engaging cavity, arranged for couplingat the first construction tube;

a second joint member arranged for coupling at the second constructiontube, wherein the second joint member is received at the engaging cavityto frictionally couple with the first joint member, such that the secondjoint member serves as a supporting shaft for supporting between the twoconstruction tubes and serves as a rotatable shaft to enable the secondjoint member to be rotated at the first joint member for a pivotalmovement between the two construction tubes; and

a connecting member extended from the second joint member through thefirst joint member to ensure an engagement therebetween.

Still further objects and advantages will become apparent from aconsideration of the ensuing description and drawings.

These and other objectives, features, and advantages of the presentinvention will become apparent from the following detailed description,the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a foldable chair according to apreferred embodiment of the present invention.

FIG. 2 is a perspective view of the foldable chair according to theabove mentioned preferred embodiment of the present invention,illustrating the supporting frame pivotally coupled with the seat framevia the reinforcing joints.

FIG. 3 is a perspective view of the foldable chair according to theabove mentioned preferred embodiment of the present invention,illustrating the construction tubes of the supporting frame and the seatframe being connected by the reinforcing joint.

FIG. 4 is a sectional view of the reinforcing joint of the foldablechair according to the above mentioned preferred embodiment of thepresent invention, illustrating the configurations of the first andsecond joint members.

FIG. 5 is a sectional view of the reinforcing joint of the foldablechair according to the above mentioned preferred embodiment of thepresent invention, illustrating the first and second joint members beingfrictionally engaged with each other.

FIG. 6 is a partially perspective view of the foldable chair accordingto the above mentioned preferred embodiment of the present invention,illustrating the joint stopper.

FIG. 7 is a perspective view of the joint stopper of the foldable chairaccording to the above mentioned preferred embodiment of the presentinvention.

FIG. 8 is a sectional view of the joint stopper of the foldable chairaccording to the above mentioned preferred embodiment of the presentinvention.

FIGS. 9A and 9B illustrates different alternative mode of the jointstopper of the foldable chair according to the above mentioned preferredembodiment of the present invention.

FIG. 10 is a perspective view of the foldable chair at a folded positionaccording to the above mentioned preferred embodiment of the presentinvention.

FIG. 11 is a side view illustrating the foldable chairs being stackedwith each other according to the above mentioned preferred embodiment ofthe present invention.

FIG. 12 illustrates the user sitting on the foldable chair according tothe above mentioned preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description is disclosed to enable any person skilled inthe art to make and use the present invention. Preferred embodiments areprovided in the following description only as examples and modificationswill be apparent to those skilled in the art. The general principlesdefined in the following description would be applied to otherembodiments, alternatives, modifications, equivalents, and applicationswithout departing from the spirit and scope of the present invention.

Referring to FIGS. 1 and 2 of the drawings, a foldable chair accordingto a preferred embodiment of the present invention is illustrated,wherein the foldable chair comprises a foldable frame constructed by aplurality of construction tubes, wherein each of the construction tubesis made of rigid material such as metal, and is configured to have arectangular cross section or circular cross section. In particular, thefoldable frame comprises a supporting frame 10, a seat frame 20, and oneor more reinforcing joints 30.

As shown in FIG. 2, the supporting frame 10 comprises a front leg frame11 and a rear leg frame 12. The front leg frame 11 comprises two frontlegs 111 which are two construction tubes. The rear leg frame 12comprises two rear legs 121 which are also two construction tubes. Thefoldable frame further comprises a back support frame 13 which comprisestwo back support members 131 integrally and upwardly extended from thefront legs 111 respectively. Accordingly, the foldable frame is adaptedto move between a folded position that the rear legs 121 are moved andparallelly extended to the front legs 111 respectively to support theseat frame 20 at a vertical manner as shown in FIG. 1, and an unfoldedposition that the front and rear legs 111, 121 are moved at apredetermined angle to support the seat frame 20 at a horizontal manner,as shown in FIG. 10.

The seat frame 20 is constructed by a U-shaped construction tubedefining two parallel side seat members 21 and a rear seat support 22integrally extended between two rear ends of the seat members 21.Accordingly, the reinforcing joints 30 are pivotally coupled the twoseat members 21 of the seat frame 20 with the front legs 111 of thesupporting frame 11 respectively. It is appreciated that the reinforcingjoints 30 are pivotally coupled the two side seat members 21 of the seatframe 20 with the rear legs 121 of the supporting frame 11 respectively.

As shown in FIG. 2, the foldable frame further comprises two guidingarms 15, wherein each of the guiding arms 15 has one end affixed at thefront leg 111, and an opposed end affixed on the rear leg 121. When thefoldable chair is moved to the folded position, the rear legs 121 of thefoldable frame 10 are guided by the guiding arms 15 to pivotally movetoward the front legs 111. In addition, when the foldable chair is movedto the unfolded position, the rear legs 121 are guided to pivotally moveaway with respect to the front legs 111 by the guiding arms 15.

The foldable chair further comprises a seat panel 23 supported by theseat frame 20 and a back panel 14 supported by the back support members131 of the back support frame 13. Accordingly, a rear edge portion ofthe seat panel 23 is supported by the rear seat support 22 of the seatframe 20 and two side edge portions of the seat panel 23 are supportedby the two side seat members 21 of the seat frame 20. In other words,the front edge portion of the seat panel 23 is suspendedly supported bythe seat frame 20. In particular, the seat panel 23 is ergonomicallydesign to ensure the sitting posture of the user. The seat panel 23 hasa butt supporting portion 231 formed indentedly and thigh supportingportion 232 frontwardly extended from the butt supporting portion 231.When the user sits on the seat panel 23, the butt and thighs of the userwill be supported by the butt supporting portion 231 and the thighsupporting portion 232 to ensure the proper sitting posture of the userin which the back of the user is straight and supported by the backpanel 14. The thigh supporting portion 232 has an upward curvingconfiguration to substantially match with the shape of the thigh of theuser. It is worth mentioning that the thigh supporting portion 232 ofthe seat frame 20 is defined at the front portion thereof, wherein thethigh supporting portion 232 is suspendedly supported by the seat frame20, such that the thigh supporting portion 232 is free from the seatframe 20 to provide a predetermined flexibility so as to generate anupward bounding force to the thighs of the user. Preferably, the seatpanel 23 is made of mesh fabric or mesh plastic for enhancing the aircirculation. When the user sits on the foldable chair, as shown in FIG.12, the butt supporting portion 231 and the thigh supporting portion 232of the seat panel 23 will support the butt and thighs of the user. Inaddition, the weight of the user will be applied on the seat panel 23 ata position that a center of mass of the user will be located on the seatframe 23 between a first connection point at the side seat members 21coupled to the rear leg 121 and a second connection point at the sideseat members 21 coupled to the front leg 111. Therefore, the foldablechair is able to support the weight of the user and to ensure thesitting posture of the user.

As shown in FIGS. 3 to 5, the reinforcing joint 30 is arranged forpivotally connecting the supporting frame 10 with the seat frame 20,wherein the reinforcing joint 30 comprises a first joint member 31coupled at the seat frame 20, a second joint member coupled at thesupporting frame 10 to frictionally engage with the first joint member31, and a connecting member 33 extended from the second joint member 32through the first joint member 31 to ensure an engagement therebetween.

The first joint member 31 has an engaging cavity 311 that the secondjoint member 32 is received at the engaging cavity 311. In particular,the first joint member 31 has a tubular shape defining the engagingcavity 311 therein, such that the second joint member 32 is insertedinto the engaging cavity 311. Once the second joint member 31 isreceived in the engaging cavity 311, an outer circumferential surface ofthe second joint member 32 is frictionally engaged with an innercircumferential surface of the engaging cavity 311 of the first jointmember 31.

In order to enhance the friction between the first and second jointmembers 31, 32, the engaging cavity 311 has a conical shape that a sizeof the engaging cavity 311 is gradually increasing from the seat frame20 to form an enlarged opening. Correspondingly, the second joint member32 has a conical shape having a size gradually reducing from thesupporting frame 10 to fit into the engaging cavity 311 through theenlarged opening thereof. In particular, a depth of the engaging cavity311 matches with a length of the second joint member 32.

Therefore, when the second joint member 32 is received in the engagingcavity 311, the first and second joint members 31, 32 serve as asupporting shaft to support between the supporting frame 10 and the seatframe 20 for effectively distributing a loading force from the seatframe 20 to the supporting frame 10. In other words, when the user sitson the seat frame 20, the loading force, i.e. the weight of the user,will transfer to the supporting frame 10 through the first and secondjoint members 31, 32. Since the second joint member 32 is a solid andrigid member, the second joint member 32 forms a supporting shaft toreplace the conventional rivet to support the foldable chair.Furthermore, the first and second joint members 31, 32 also serve as arotatable shaft to enable the second joint member 32 to be rotated atthe first joint member 31 within the engaging cavity 311 thereof for apivotal movement between the supporting frame 10 and the seat frame 20.

As shown in FIGS. 3 to 5, the first joint member 31 is sidewardlyextended from the seat member 21 of the seat frame 20 and the secondjoint member 32 is sidewardly extended from the front leg 111 of thesupporting frame 10. For pivotally connecting the seat frame 20 with therear leg frame 12, the first joint member 31 is sidewardly extended fromthe seat member 21 of the seat frame 20 and the second joint member 32is sidewardly extended from the rear leg 121 of the supporting frame 10.

It is worth mentioning that no washer is required for coupling betweenthe supporting frame 10 and the seat frame 20. Since the second jointmember 32 has a predetermined length to be received in the engagingcavity 311 of the first joint member 31, the distance between the twoconstruction tubes, i.e. the seat member 21 and the front leg 111, canbe substantially retained by the length of the second joint member 32.Therefore, the seat frame 20 can only be pivotally moved with respect tothe supporting frame 10 via the reinforcing joint 30 to prevent anyunwanted lateral movement therebetween during the folding and unfoldingoperations and especially when the foldable chair is moved at theunfolded position for the user to sit thereon.

According to the preferred embodiment, the connecting member 33 isembodied as a rivet to couple between the first and second joint members31, 32. However, the connecting member 33 is not used for supporting thefolding chair. In other words, since the loading force will betransferred to the first and second joint members 31, 32, the loadingforce will not be applied to the connecting member 33. It is appreciatedthat the connecting member 33 can be a screw or other fasteningelements.

Accordingly, the supporting frame 10 has a first coupling hole 101 andthe seat frame 20 has a second coupling hole 201 aligned with the firstcoupling hole 101, wherein the first and second coupling holes 101, 201is slightly larger than a diameter of the connecting member 33. Theconnecting member 33 has two ends rotatably coupled at the first andsecond coupling holes 101, 201 through the first and second jointmembers, 31, 32. It is worth mentioning that the second joint member 32has a through channel 320 aligned with the first and second couplingholes 101, 201, such that the connecting member 33 extended between thefirst and second coupling holes 101, 201 through the through channel 320of the second joint member 32. It is appreciated that the connectingmember 33 can be integrally extended from the second joint member 32 toengage with the first coupling hole 101 after the second joint member 32is received in the engaging cavity 111 of the first joint member 31,such that no second coupling hole 201 and the through channel 320 willbe required.

As shown in FIGS. 4 and 5, the reinforcing joint 30 further comprises afirst attachment panel 34 and a second attachment panel 35 securelyaffixing to the seat frame 20 and the supporting frame 10 respectively,wherein the first and second joint members 31, 32 are integrallyextended from the first and second attachment panels 34, 35respectively.

Accordingly, the first attachment panel 34 has a first attachmentsurface configured to match with a contour of the seat member 21 of theseat frame 20, wherein the first attachment surface of the firstattachment panel 34 is affixed to the seat member 21 of the seat frame20. Likewise, the second attachment panel 35 has a second attachmentsurface configured to match with a contour of the front leg 111 of thesupporting frame 10, wherein the second attachment surface of the secondattachment panel 35 is affixed to the front leg 111 of the supportingframe 10. Therefore, the reinforcing joint 30 can be incorporated withthe two construction tubes with different cross sections. It is worthmentioning that the first attachment panel 34 and a second attachmentpanel 35 are securely affixed to the seat frame 20 and the supportingframe 10 respectively via fasteners, such as pins or nails. In addition,the first and second attachment panels 34, 35 will enlarge the forcetransmitting surfaces for the seat frame 20 and the supporting frame 10to enhance the loading force to effectively transmit from the seat frame20 to the supporting frame 10.

When the foldable chair is moved between the unfolded position and thefolded position, the rear legs 121 are pivotally moved with respect tothe front legs 111, such that the second joint member 32 is frictionallyrotated within the engaging cavity 311 of the first joint member 31. Itis worth mentioning that the frictional engagement between the first andsecond joint members 31, 32 will generate the frictional force to retainthe foldable chair at the folded position. In other words, the user mustapply the force to overcome the frictional force in order to move thefoldable chair from the folded position to the unfolded position.Likewise, the frictional engagement between the first and second jointmembers 31, 32 will generate the frictional force to retain the foldablechair at the unfolded position to prevent the foldable chair from beingfolded accidentally.

It is worth mentioning that the reinforcing joint 30 of the presentinvention is able to pivotally connect two construction tubes of anyfoldable furniture, such as foldable table. In addition, the reinforcingjoint 30 can also connect two construction tubes of the foldable chairat any location for pivotal movement. Accordingly, the reinforcing joint30 can solve the problems of the existing rivet connection structure forpivotally connecting two construction tubes. The width of thereinforcing joint 30 will retain the distance between the constructiontubes to stabilize the structure of the foldable frame to prevent anyunwanted lateral movement between the construction tube. The reinforcingjoint 30 is more rigid than the rivet to support the foldable frame andto effective distribute the loading force. Since the first and secondjoint members 31, 32 are frictionally engaged with each other, there isno clearance formed therebetween to create any wobbling movement of thefoldable chair especially when it is unfolded.

As shown in FIG. 6, the rear legs 121 of the rear leg frame 12 arepivotally folded at the unfolded position that two upper ends of therear legs 121 are biased against the back support members 131respectively, such that the front and rear legs 111, 121 are moved atthe predetermined angle. In particular, the supporting frame 10 furthercomprises a joint stopper 16 coupled at an upper end of the rear legframe 12 for biasing against the back frame 13 to retain the foldableframe at the unfolded position. Accordingly, two joint stoppers 16 arecoupled at the upper ends of the rear legs 121 respectively, whereineach of the joint stoppers 16 has a stopping surface 161, as a frontstopping surface, biased against the corresponding back supportingmember 131 to ensure the foldable frame at the unfolded position.Accordingly, the contour of the stopping surface 161 matches with thecontour of the rear side of the back supporting member 131 formaximizing the contacting area therebetween. For example, when the backsupporting member 131 has a circular cross section, the stopping surface161 will be configured to have an arc-shaped surface to substantiallybias against the rear side of the back supporting member 131. In oneembodiment, the stopping surface 161 has a concave configuration to biasagainst the rear side of the back supporting member 131.

Each of the joint stoppers 16 further has a joining surface 162, as arear joining surface, formed opposite to the stopping surface 161, asshown in FIG. 8. For example, the stopping surface 161 is formed at afront side of the joint stopper 16 and the joining surface 162 is formedat a rear side of the joint stopper 16. Accordingly, the joint surfaces162 of the joint stoppers 16 are arranged for coupling with the backsupporting members 131 of another foldable chair so as to stack thefoldable chairs with each other. In other words, the joint stoppers 16also serve as stackable joints for retaining the foldable chairs to bestacked with each other. In particular, when the foldable chair isfolded, the front and rear legs 111, 121 are moved to each otherside-by-side, such that the joint surfaces 162 of the joint stoppers 16face rearwardly when the foldable chair is folded. Therefore, when twofolded foldable chairs, i.e. the first folded chair and the secondfolded chair, are stacked with each other, the joint surfaces 162 of thejoint stoppers 16 of the first folded chair are detachably coupled withthe back supporting members 131 of the second folded chair, so as toretain the folded chairs in a stacked manner, as shown in FIG. 11. It isappreciated that multiple folded chairs can be stacked with each otherand can be interlocked with each other to retain the folded chairs in astacked manner.

It is worth mentioning that the contour of the joining surface 162matches with the contour of the front side of the back supporting member131 for maximizing the contacting area therebetween when two foldablechairs are stacked. In one embodiment, the joining surface 162 has aconcave configuration to bias against the front side of the backsupporting member 131 of another foldable chair.

According to the preferred embodiment, each of the joint stoppers 16further comprises an inner join wall 163 and an outer join wall 164spacedly and rearwardly extended to define the joint surface 162 betweenthe inner and outer join walls 163, 164. In particular, the inner andouter join walls 163, 164 are rearwardly extended from two sidewalls ofthe joint stopper 16 respectively. In other words, the back supportingmember 131 of second folded chair will engage with the joining surface162 of the joint stopper 16 between the inner and outer join walls 163,164.

Preferably, a height of the outer join wall 164 is larger than a heightof the inner join wall 163. Therefore, the two outer join walls 164 ofthe joint stoppers 16 of each of the foldable chair form two boundarywalls to guide and couple the back supporting member 131 of secondfolded chair so as to retain the foldable chairs in a stacked manner.Preferably, each of the outer join walls 164 has a trapezoid shape andeach of the inner join walls 163 has a rectangular shape. Preferably,one side edge of the outer join wall 164 is a slanted side edge andanother side edge of the outer join wall 164 is a curved side edge. Itis appreciated that the height difference between the outer joint wall164 and the inner joint wall 163 can be modified and the shape of theouter joint wall 164 and the inner joint wall 163 can be altered asshown in FIGS. 9A and 9B.

In one embodiment, in order to couple the joint stoppers 16 at the upperends of the rear legs 121 respectively, each of the joint stoppers 16further comprises an joint connector 165 extended downwardly to slidablyinsert into the upper end of the rear leg 121, as shown in FIG. 7.Preferably, each of the rear legs 121 has tubular shape defining anupper opening at the upper end of the rear leg 121, wherein the jointconnector 165 is inserted into the rear leg 121 through the upperopening thereof. It is appreciated that the joint stopper 16 can beincorporated with any existing folding chair to provide multiplefunctions of retaining the foldable chair at the unfolded position bybiasing against the back supporting members 131 of the foldable chairand retaining the foldable chairs at a stacked position by engaging withthe back supporting members 131 of another foldable chair.

One skilled in the art will understand that the embodiment of thepresent invention as shown in the drawings and described above isexemplary only and not intended to be limiting.

It will thus be seen that the objects of the present invention have beenfully and effectively accomplished. The embodiments have been shown anddescribed for the purposes of illustrating the functional and structuralprinciples of the present invention and is subject to change withoutdeparture from such principles. Therefore, this invention includes allmodifications encompassed within the spirit and scope of the followingclaims.

What is claimed is:
 1. A foldable chair, comprising: a foldable framewhich comprises a supporting frame and a seat frame; and at least onereinforcing joint for pivotally connecting said supporting frame withsaid seat frame, wherein said reinforcing joint comprises: a first jointmember, having an engaging cavity, coupled at said seat frame; a secondjoint member coupled at said supporting frame and received at saidengaging cavity to frictionally couple with said first joint member,wherein said first and second joint members serve as a supporting shaftto support between said supporting frame and said seat frame and serveas a rotatable shaft to enable said second joint member to be rotated atsaid first joint member for a pivotal movement between said supportingframe and said seat frame; and a connecting member extended from saidsecond joint member through said first joint member to ensure anengagement therebetween.
 2. The foldable chair, as recited in claim 1,wherein said first joint member has a tubular shape defining saidengaging cavity therein, such that said second joint member is insertedinto said engaging cavity at a position that an outer circumferentialsurface of said second joint member is frictionally engaged with aninner circumferential surface of said engaging cavity.
 3. The foldablechair, as recited in claim 2, wherein said engaging cavity is a conicalcavity and said second joint member has a corresponding conical shape toenlarge a frictional contacting area between said first joint member andsaid second joint member.
 4. The foldable chair, as recited in claim 3,wherein a depth of said engaging cavity matches with a length of saidsecond joint member.
 5. The foldable chair, as recited in claim 1,wherein said supporting frame has a first coupling hole and said seatframe has a second coupling hole, wherein said connecting member has twoends rotatably coupled at said first and second coupling holes throughsaid first and second joint members.
 6. The foldable chair, as recitedin claim 4, wherein said supporting frame has a first coupling hole andsaid seat frame has a second coupling hole, wherein said connectingmember has two ends rotatably coupled at said first and second couplingholes through said first and second joint members.
 7. The foldablechair, as recited in claim 1, wherein said reinforcing joint furthercomprises a first attachment panel and a second attachment panelsecurely affixing to said seat frame and said supporting framerespectively, wherein said first and second joint members are integrallyextended from said first and second attachment panels respectively. 8.The foldable chair, as recited in claim 6, wherein said reinforcingjoint further comprises a first attachment panel and a second attachmentpanel securely affixing to said seat frame and said supporting framerespectively, wherein said first and second joint members are integrallyextended from said first and second attachment panels respectively. 9.The foldable chair, as recited in claim 1, wherein said supporting framecomprises a front leg frame and a rear leg frame, wherein said seatframe is pivotally coupled at said front and rear leg frames via saidreinforcing joints respectively.
 10. The foldable chair, as recited inclaim 8, wherein said supporting frame comprises a front leg frame and arear leg frame, wherein said seat frame is pivotally coupled at saidfront and rear leg frames via said reinforcing joints respectively. 11.The foldable chair, as recited in claim 9, wherein said supporting framefurther comprises a back frame upwardly extended from said front legframe, and a joint stopper coupled at an upper end of said rear legframe, wherein said joint stopper has a front stopping surfaceconfigured for biasing against said back frame to retain said foldableframe at an unfolded position and a rear joining surface arranged insuch a manner that when two of said foldable chairs are stacked witheach other, said rear joint surface of one foldable chair is engagedwith said back frame of another foldable chair so as to retain saidfoldable chairs in a stacked manner.
 12. The foldable chair, as recitedin claim 10, wherein said supporting frame further comprises a backframe upwardly extended from said front leg frame, and a joint stoppercoupled at an upper end of said rear leg frame, wherein said jointstopper has a front stopping surface configured for biasing against saidback frame to retain said foldable frame at an unfolded position and arear joining surface arranged in such a manner that when two of saidfoldable chairs are stacked with each other, said rear joint surface ofone foldable chair is engaged with said back frame of another foldablechair so as to retain said foldable chairs in a stacked manner.
 13. Thefoldable chair, as recited in claim 12, wherein said front stoppingsurface and said rear joining surface are configured to have a contourmatching with a contour of a rear side of said back frame and a contourof a front side of said back frame respectively.
 14. A reinforcing jointfor pivotally connecting first and second construction tubes of afoldable chair, comprising: a first joint member, having an engagingcavity, arranged for coupling at the first construction tube; a secondjoint member arranged for coupling at the second construction tube,wherein said second joint member is received at said engaging cavity tofrictionally couple with said first joint member, such that said secondjoint member serves as a supporting shaft for supporting between the twoconstruction tubes and serves as a rotatable shaft to enable said secondjoint member to be rotated at said first joint member for a pivotalmovement between the two construction tubes; and a connecting memberextended through said first joint member and said second joint member toensure an engagement therebetween.
 15. The reinforcing joint, as recitedin claim 14, wherein said first joint member has a tubular shapedefining said engaging cavity therein, such that said second jointmember is inserted into said engaging cavity at a position that an outercircumferential surface of said second joint member is frictionallyengaged with an inner circumferential surface of said engaging cavity.16. The reinforcing joint, as recited in claim 15, wherein said engagingcavity is a conical cavity and said second joint member has acorresponding conical shape to enlarge a frictional contacting areabetween said first joint member and said second joint member.
 17. Thereinforcing joint, as recited in claim 14, wherein a depth of saidengaging cavity matches with a length of said second joint member. 18.The reinforcing joint, as recited in claim 16, wherein a depth of saidengaging cavity matches with a length of said second joint member. 19.The reinforcing joint, as recited in claim 14, further comprising afirst attachment panel and a second attachment panel for securelyaffixing to said seat frame and said supporting frame respectively,wherein said first and second joint members are integrally extended fromsaid first and second attachment panels respectively.
 20. Thereinforcing joint, as recited in claim 18, further comprising a firstattachment panel and a second attachment panel for securely affixing tosaid seat frame and said supporting frame respectively, wherein saidfirst and second joint members are integrally extended from said firstand second attachment panels respectively.
 21. A foldable chair,comprising: a foldable frame which comprises a supporting frame and aseat frame, wherein said supporting frame comprises a front leg frame, arear leg frame and a back frame upwardly extended from said front legframe; at least a joint pivotally coupled at said front leg frame andsaid rear leg frame for pivotally connecting said supporting frame withsaid frame such that said foldable frame is adapted to move between afolded position that said supporting frame supports said seat frame at avertical manner, and an unfolded position that said support frame ismoved at a predetermined angle to support said seat frame at ahorizontal manner; and a joint stopper, which is coupled at an upperportion of said rear leg frame, having a front stopping surfaceconfigured for biasing against said back leg frame to retain saidfoldable frame at said unfolded position and a rear joining surfacearranged in such a manner that when two of said foldable chairs arestacked with each other, said rear joint surface of one of said foldablechairs is engaged with said back frame of another said foldable chair soas to retain said foldable chairs in a stacked manner.
 22. The foldablechair, as recited in claim 21, wherein said front stopping surface andsaid rear joining surface are configured to have a contour matching witha contour of a rear said of said back frame and a contour of a frontside of said back frame respectively.